Support for direct D2D communication as an integrated part of a wireless communication network is currently being considered for the further evolution of LTE networks. With direct D2D communication, user equipment (UE) may communicate directly with each other without involvement of a base station or an enhanced node B (eNB). One issue with D2D communication is device discovery to enable D2D communications. Device discovery involves discovering one or more other discoverable UEs within communication range for D2D communication. Device discovery also involves being discovered by one or more other discovering UEs within communication range for D2D communications. There are many unresolved issues with respect to device discovery for D2D communication including the signaling used for device discovery and the discovery information conveyed during device discovery.
One issue with D2D discovery and D2D communication is interference with the communications of the cellular network (e.g., communications between a UE and an eNB). This is particularly an issue since the power level of D2D signals may not controlled by an eNB. For D2D discovery, UEs may desire to transmit discovery signals at maximum transmit power to increase the probability of being discovered by other devices. As a consequence of the discovery signal transmissions not being power controlled to the eNB, there may be significant impact from interference due to in-band emissions (IBE) due to the non-ideal characteristics of RF components and modulation process. Additional asynchronous interference may also result due to transmission time mismatch between uplink cellular transmissions which are transmitted with an application of a timing advance (TA) and D2D discovery signal transmissions which are transmitted without a timing advance (i.e., since discovery signal transmissions may be from UEs that are idle mode that do not have any assigned TA).
Thus there are general needs for devices and methods that reduce interference from D2D discovery and D2D communications. There also are general needs for devices and methods for transmit power control (TPC) for D2D discovery and D2D communications. There also are general needs for devices and methods to control the level of interference from D2D discovery signals.